Chine walk question
 

I just added 800 HP to my 27' Cobra V bottom. I am seeing a little chine walk at about 80 mph 4200 rpm. I have a lot of power left but I keep backing out when i feel a little chine walk. My question is how much chine walk is ok before i back out? I have trim tabs and full hyd steering. I have been driving boats for 15 years but never a V bottom over 80 mph. Can a 27' V bottom do over 90 mph without chine walk?Thanks for the advice.

Re: Chine walk question
 

at over 80 in a 27 you are going to get alittle chine walk as long as it stays gentle just drive through it however there are a few things that help you mentioned that you have tabs if they are not already put the long ones ( mercury or =) but the long 30 inch ones don't bury the tabs but run them about parallel or up alittle ( in flat water) also what prop do you run ? you can have the trailing edge eased to settle the stern talk to matt at throttle up he can help. where are your tabs mounted?
at some speed all v's will tend to start chining
good luck
Larry svl #51 wild ride

Re: Chine walk question
 

How much prop are you turning? My 272 baja v-hull has 950 hp and runs low to mid 90's with a 32 pitch labbed. It used to chinewalk from 70-75 mph when it had 750 hp but the full hyd steering got rid of 95 % of it. It will torque steer/roll from 60 to 80 now if I try to run with no weight in the boat or gas but 1/2 tk of gas or one passenger eliminates it. I'm sure your running a 4 blade prop,it makes it much worse but like my boat you probably could break a 3 blade loose at any speed with the kind of power your talking about. Labbed props seem to help too,I think the thicker blades on a non-labbed prop lift the transom more. Your steering is definately full hydraulic to the helm? Is it twin ram? I added external twin ram at first to my boat and it still chine walked terrible,the full to helm cleaned it up. What is your beam?How long are your tabs,I had cheap bennets and made stainless replacements that are twice as long. Even though I don't run with my tabs very far into the water if the boat twist back and forth they are close to the water and help to neutralize the chine walking.You might have to run with your tabs dug in hard until you reach a certain speed or find that you have to "drive thru it" because of design of your hull,Smitty

Re: Chine walk question
 

Chine walk can kill. There is a board member who several years ago added that kind of power to his Baja against the recommendations of his engine builder. I remember that builder saying "This boat is going to kill somebody." I recommemded that he not build the engine, but it was a rich contract and he needed the money. Well his prediction turned out to be pretty accurate. The members best friend spent the next couple of years in a coma and the boat was sold for it's parts-after it's second time out.

The ability to control a chine walk has as much to do with the driver as the boat. Do you just steer the boat or are you in tune with the boat? Focus on the bow. You'll see the point start to waver as the boat drops off it's pad. The boat will always drop to the right so you can twitch the wheel to the left. High speeds will result in you shooting glances to the water and back to the bow trying to read everything at once. If you get out of synch and tweek the wheel at the wrong moment you will throw the boat into a severe chinewalk that can only be corrected by chopping the throttle and puckering. This is super dangerous because it will be very easy to hook a chine. Please wear a impact vest and keep the passengers out of the boat until you master it.

There are some things that can be done to help reduce the chinewalk. Do the lifting strakes go all the way to the transom? If so, then removing a couple of them will help kill the lift and perhaps ballance the boat. How tight is the steering? You have FULL hydraulic, right? How tight is your gimble? That gimble had better be like a virgin, any slop will result in a chine walk at your speeds. How high is your x-dim? Lowering it will help create more bow lift and help ballance the boat. What do you use for a prop? Yea the Bravo's are fast, but a Hydromotive is super smooth. How much trim do you dial in? If you are overtrimming for the speed, you could be driving the boat out of the water. The final easy fix is to drag tab. This will slow the boat, but it provides a larger area for the boat to ballance on. Just don't attempt to adjust the tabs at speed. A errant adjustment could result in the loss of control.

The ultimate fix? Pull your engine out and stab it into a cat. You'll go 10mph faster and can do it one handed while talking to your passengers. Believe me, cats are that good. They really are.

Re: Chine walk question
 

Or a Fountian.......

Re: Chine walk question
 

That tragic accident was in a 25 Sunsation and had nothing to do with chine walking. He hit a big wave wrong going to fast and hooked the boat.

Re: Chine walk question
 

Thank you all for the info. I do have dual ram full hyd steering. I will check for play. i am running a 4 blade 28 pitch prop. I haven't had a chance to run to my max rpm so I'm sure i will be changing props. I have victory trim tabs but I'm not sure of the size. they look at least 20". The tabs follow the bottom of the hull about 4" in from the outside edges. (Cord )I will check my X dimension and get back to you. if i start to chine walk to hard and i back off the throttle to hard what will happen? if i drop the tabs to much what will happen (besides loss of speed) I am only getting a slow rocking back and forth but before i hurt someone i want to ask all the questions. PS: I will be putting this motor in a cat next year.

Re: Chine walk question
 

Larry, Are you saying to not drop my tabs at all? How do they keep you stable if they aren't down? by the way i was testing on water like glass. I would hold the steering wheel stable. maybe thats my problem. maybe i should play with the steering a little.

Re: Chine walk question
 

I wouldn't be too concerned about a slow rocking motion, so long as it stays slow. Glass water will bring out the worst in chine walking. So will holding the wheel still. Before you do anything, try steering the chine walk, get a feel for it and slowly push the throttle forward. See my above post for the steering. Your later posts make the problem sound better than your first one.

Dropping the tabs too far won't cause anything too dramatic - so long as you are not going fast. Don't drop the tabs at speed because you could loose control if something isn't just right. Back off and adjust them and then speed back up and see what happens. Later when you are very familiar with the new power and how the boat reacts to it you can try adjusting the tabs at speed.

Re: Chine walk question
 

I have a Checkmate 230 Enforcer with about 550 hp in it and it starts to chinewalk BAD at 75 mph so I just end up counter-steering against the chinewalk to kep the boat balanced on the keel... It took a little practice but eventually I did get the hang of it :D

I've heard that Throttle up can also modify your prop to help some also...

Doug

Re: Chine walk question
 

Chine walking can be 'controlled' to a point. On hipo outboards, they have hotfoot throttles and trim controls on the steering wheel for this very reason.

Takes practice at the higher limits of chinewalking with small inputs of throttle, trim, and steering.

Re: Chine walk question
 

I currently have a chine walking problem with my 32' Active Thunder just after hitting about the 83mph mark. I have full external race steering, stock/standard length Bravo One drives (no nose cones) hung on Stellings extension boxes with lab finished Bravo One 4-bladed 32" props. The boat had a pretty good hook in the bottom that was removed. Measuring from the propshaft centerline, my drives sit about 3.5-4.0" below the bottom of the boat. I have the extra long K-Plane trim tabs and give it only enough tab just to take the chine walk out, but at the expense of speed. I have purchased some -2" IMCO shorty lowers that I am going to try in hopes that it might help with the chine walk problem---but as with anything else I guess we'll see.

By the way, this usually happens in dead calm, or relatively calm water conditions.

Re: Chine walk question
 

first even at level the spray hitting the tabs helps, if your tabs are the 20" ones put on the 30's theywon't scrub as much speed ( you will have to put the 20" down more to get the same result) what you have to remember is on V bottom boats the faster you go the more the boat comes up out of the water and basically falls off its V less to balance on as speed increases ( and yes boats with pads have a wider balance area) the trade off is a harder ride depending how flat the pad is for example fountain has a deadrise to thier pad so is sort of a compromise whereas early velocity 30's ( a fast hull) had a flat pad and keep in mind the shorter lighter boat is going to get high in the water at a lower speed than a bigger boat. the prop work I mentioned works by letting the stern sink which will help the chine ( wider area in water to balance on) we test these things on the race boat on dead flat water so you can see consistant results ( alittle chop and the boat never chines) the longer tabs act like training wheels or out riggers and trust me they will help even at level if you start putting them down in calm water you will scrub alot of speed ( although with all your power you could run the drive in bury the tabs and just power though ) not very efficent
the gentle rock I wouldn't worry about all the phantoms and extreams do that someone even coined the phrase the "phantom dance " refering to that. at some point unfortunatly you will just run out of bottom and will be at a speed barier. obviously cats and tunnel boats and 3 points extend that threshold by widening there stance

Re: Chine walk question
 

That may depend on the hull. My hull is the opposite. I chine walk more with a 3 blade.

Re: Chine walk question
 

I know this is nuts but when we used to run the factory boats my guys used to set up the bottoms so that they would chine walk at full speed conditions I was in the boat several times with them and they used to drive the chine walk out with the steering by counter steering and they claimed the boat was faster that way it was a hairy ride but it did run awesome we set a couple of kilo records and that wasn't bad at the time with an independent team with no factory sponsorship. Also from my experience I know many guys say to run the other drives on the market the Bravo lower was the fastest lower we ever ran we took a Bravo of one day three times and installed another drive to not mention the name and lost 3.5 mph on gps the y may be stronger and everything else but they are also slower maybe someone else has had the same problem. Good Luck Laz Mesa

Re: Chine walk question
 

I was thinking just the opposite. I thought that choppy water would start the chine by rocking my boat side to side. I was also thinking that the harder i held the steering straight the better. Thats why I'm never afraid to ask questions. I'm sure a lot of people reading this thought the same thing.

Re: Chine walk question
 

there are many things you can do to help get rid of some of the walk. other than that if it is walking at 80 mph and you don't know how to stop it, you are running the risk of severely hurting yourself and anyone around you. you really should get yourself comfortable steering that walk out of the boat. it will make you a better driver. anyone who drives a fast v-hull needs to have some experience before just nailing the throttle. cats are more forgiving, but to some degree that is just a false sence of security before the boat gets away from you. by the way. ever been upside down in a boat at over 80? trust me it hurts. and if you are lucky enough to walk away, 20 years later it still hurts sometimes.

Re: Chine walk question
 

It is possible that you are experiencing this because you are running at 4200 RPM which may be close to your peak torque. Therefore torque loading and potentially causing ill behaviors. So combating them and softening them would be the objective.

Julie

Re: Chine walk question
 

Julie, Thanks for the reply. But my peak torque is at 4700 rpm and 850 lbs torque. I will be calling you soon for a lab finish prop.

Re: Chine walk question
 

Cobra 1,
Is the 80 MPH a new top speed? If so, you may be " running out of bottom" cause by the increased hull lift. In other words, you are only running on the flat part of the hull bottom without the inter strakes touching the water. I suggest you hang the boat on one strap and find the balance point (CG). If the inter strakes are equal to or forward of this point, you may not be able to get control of the chine walk until you lengthen the inter strakes. If the bottom set-up is right/perfect, i believe you should be able to reasonable control a 27" vee to 90-100MPH.

Re: Chine walk question
 

Thanks Benperfected. How much is involved in extending the inter starkes? without doing this can tabs do the same thing? The good thing is i am not worried about loosing speed by dropping my tabs. I have a lot of power left. If anyone knows someone in the lake Havasu area that can help me with checking out my hull,let me know.

Re: Chine walk question
 

Chine walk is actually, more balance related than enviromental. You need to balance the boat on the pad. The problem is that your boat is falling off of this point. When the ball falls over the lifting strakes contact the water and produce lift. The lift pushes the hull up and it tips over it's balance point to the other side and thus starts a chain reaction. This reaction will continue to get more violent until something changes. Dragging tab gives you two out riggers for support, but the drag will slow you down. Glassy water never provides any lift for the strakes so the boat is truly balanced on it's pad which is why this problem shows up more often in glassy water. When the boat starts to fall off, a slight steering correction will help to tip it back up right. It's like riding your bike at slow speed. Yea, you could put training wheels on so that anybody can ride the bike, but you'll never go fast [and turn]. Or you can learn how to balance the bike. You know that if you start to tip over, you two basic choices. You can put your foot down and push the bike back upright, but if you are going fast this could push the bike over for a painful crash. This is just like the lifting strakes hiting the water. The second choice is to adjust the steering so the bike stays balanced. With a little practice the minor steering adjustments become auctiomatic. You are trying to do the same thing with your boat.

Before labbing your prop, try a Hydromotive Q4. The Q4 has less bow lift than the Bravo and that really helps calm the chine walk down.

Re: Chine walk question
 

Thanks Cord. Well said.

Re: Chine walk question
 

Cord, Ditto to what Cobra said. That is the best explaination I've seen.

Makes me itch to get the ol' Hydrostream out and do some 'walkin :eek: :eek: :evilb: :evilb: :evilb:

Re: Chine walk question
 

That answered my problem........ :evilb: My boat does it really bad when I run a bravo 1. It all goes away when I put a mirage plus on. But its one of those give and take situations.

Learn a lot today from this post :drink:

Re: Chine walk question
 

When I had my 25 Eagle, I started to get a chine walk at 80, I could steer the boat ever so slightly to the left or was it the right and it would go away. Was I under control? No. I think thinning the blades on the propeller would help. Longer properly placed tabs would help. But if your just in it for this year why spend the cash? Maybe you could go ask some of the bass boat guys, they are experts at handling chine walk.